Leaf Beetle Key To Ridding S. Florida Of Destructive Vine

MIAMI (CBSMiami) — The newest weapons in Florida’s long and mostly losing war against exotic plants seemed in no real rush to enter the fray on Friday, clinging to their plastic containers, the hands of young students and the shirt of entomologist Ted Center.

“They’re very hardy. You can handle them,” instructed Center, pinching a bug just a little bigger than a grain of rice between his fingers and then reaching out to let it fly off into the lush forest surrounding Long Key Natural Area in Davie.

It promptly dropped straight down into the dirt.

In its article, CBS4 news partner The Miami Herald reports it was just a natural defense reaction of the air potato leaf beetle, the latest pest-fighting “bio-control agent’’ unleashed by researchers from the U.S. Department of Agriculture’s Invasive Plant Research Laboratory in Fort Lauderdale.

The beetle, formally known as Lilioceris cheni, soon flittered away with some 200 others in search of air potato, a vine that may sound like a diet food product but ranks among the state’s most damaging, difficult-to-control pest plants.

Judging by the results of earlier test releases across South Florida, the beetle may offer the first real hope of knocking back the notoriously resilient air potato, which can climb 60 feet and smother everything from wild coffee bushes to live oak trees in a dense, strangling cloak.

The air potato, an inedible variety of yam originally from Asia, spreads by dropping gnarled potato-like growths called bulbils that can grow up to two-pound-plus, Idaho-baking size.

Though not as well-known as the melaleuca or Brazilian pepper, it’s equally problematic and found across the state and Gulf Coast. It is particularly dense in South Florida, where air potato has overtaken tropical hammocks in parks and wild areas.

In Miami-Dade County, for instance, air potato has infested just over half the 90 sites maintained by the county, said natural areas manager Joe Maguire. Fighting it is a frustrating, expensive exercise that can run more than $8,000 an acre.

Periodic clean-up efforts by volunteer “spud-busters,” followed by herbicide treatments, barely hold ground. “You think you’ve done a great job and you come out the next March or April and it’s all back again,” he said.

Like many exotic pests, the air potato was brought to Florida as an ornamental plant around 1905. Its rapid growth and heart-shaped leaves made it attractive.

Pat Howell, a Broward County natural area specialist at Tree Tops Park, said homeowners didn’t initially realize how damaging they were — and some still don’t.

“They liked how they twined around mailboxes,’’ she said, but “they’ll twine your whole house if you don’t do something.’’

After more than a century, with no Florida native insects to keep it in check, the air potato has run amuck. Its vines turn brown and brittle every winter.

But by spring, millions of ticking spud bombs lurking in the soil explode in a new, thicker tangle crowding out and even killing native plants. The vines, Center said, grow at an astounding rate of up to 10 inches a day.

Scientists at the USDA’s Agriculture Research Service in Fort Lauderdale went back to the air potato’s native lands in China to seek a potential “bio-control’’ — an insect that targets only a single host plant.

Though Florida has a long history of misguided imports — melaleuca to drain the Everglades, bufo toads to control sugar cane pests and blue tilapia to clear weeds in canals, to name a few — bio-controls today must clear a rigorous screening process involving multiple agencies that can take years, said Center, the lab’s research leader.

The aim is to ensure imports won’t develop an appetite for unintended plants, including crops such as citrus and sugar cane.

In the last decade, scientists at the center, with support from state and counties agencies, have introduced dozens of imported insects. Not every bio-control has worked but some, such as the melaleuca snout beetle, have put a real dent in troublesome species.

Center stressed that bio-controls are not “silver bullets’’ capable of eradicating an invasive plant but they can promise cheaper, more environmentally friendly alternatives to chemical herbicides.

In a handful of initial tests this spring, the air potato leaf beetle has shown promise.

Attractive as bugs go, its flame-colored wings standing out against a body as shiny as black patent leather, the beetle possesses a prodigious appetite, consuming by USDA estimates about 30 square feet of leaf in a three-month life span.

It also reproduces rapidly, with females laying about 1,200 eggs each cycle. There aren’t enough beetles now to do much damage but Florida’s Department of Agriculture and Consumer Services will begin mass rearing them for wider release at three labs.

At the tropical forest in Davie, just 66 of the beetles have taken a visible bite out of a small test area, leaving air potato leaves looking like they’ve been peppered by repeated shotgun blasts.

Ellen Lake, a USDA research entomologist, pointed out one native wild coffee plant, completely cloaked a few months ago, was now visible through the desiccated vine.

Though the beetles may not do enough damage to kill a vine outright, they could weaken the plant enough to limit its climbing or curb its output of bulbils.

One key, Lake said, is how well the beetles survive the winter. It could take several years and wider releases to determine effectiveness.

Still, Center is optimistic the beetles could become a new and powerful tool against a supremely stubborn pest.

He’s looking forward to next spring, when the bugs will emerge from the leaf litter and soil to find plenty of what they seem to crave most — tender new air potato shoots.

“We’ve very interested to see what will happen,’’ he said. “The hope is they’re going to devastate the foliage.’’